Hyphenation doesn't work and lines overflow with French Babel (Lyx)

I’m using texlive-babel-french (on Fedora) with Lyx, and text overflows instead of having clear cuts because of hyphenation. When I change language from French to English in Document > Preferences > Language, hyphenation works correctly, but LaTeX generated text (like Abstract) is not in French anymore, so I can’t use the english package.

Edit: a sort of minimal example. I kept all Lyx code, because I don’t know if it’s of any use.

%% LyX 2.1.2 created this file.  For more info, see http://www.lyx.org/.
%% Do not edit unless you really know what you are doing.
documentclass[12pt,a4paper,french]{article}
usepackage[T1]{fontenc}
usepackage[latin9]{inputenc}
usepackage{babel}
makeatletter
addtoextrasfrench{%
   providecommand{og}{leavevmodeflqq~}%
   providecommand{fg}{ifdimlastskip>z@unskipfi~frqq}%
}

makeatother
usepackage[unicode=true,pdfusetitle,
 bookmarks=true,bookmarksnumbered=false,bookmarksopen=false,
 breaklinks=false,pdfborder={0 0 0},backref=false,colorlinks=false]
 {hyperref}

makeatletter

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% LyX specific LaTeX commands.
pdfpageheightpaperheight
pdfpagewidthpaperwidth


makeatother

begin{document}
Les og visual guidelines fg{} étaient complètes pour les usages
abordés, et la référence de l'API (qui explique chaque méthode) explicative
et claire. La documentation, quant à elle, laissait à désirer. Tout
comme d'autres documentations the rest is private information, sorry   but you can see how the text continues without any problem. But
I have long words like documentation documentation documentation documentation
documentationdocumentation documentation documentation documentation...
end{document}